Stabilization of fatty acid derivatives



Patented Aug. 18, 1942 STABILIZATION F FATTY ACID DERIVATIVES George D.Martin, Nitro, W. Va... asslgnor to Monsanto Chemical Company, St.Louis, Mo., a corporation of Delaware No Drawing. Application April 25,1940, Serial No. 331,616

Claims.

The present invention relates to improvements in the stabilization ofcompounds containing a fatty acid radical as for example fatty acidderivatives such as vegetable oils, fats, soaps, and soap products. Moreparticularly this invention relates to the stabilization of soap or soapproducts made from fats which ordinarily deteriorate or developrancidity in a relatively short time.

Among the objects of the present invention is the inhibiting orretarding the deterioration of soap and soap products or similarsubstances.

Another object is the preparation of an improved vegetable oil or soap.A particular object of the invention is to stabilize both as to colorand odor the salts of higher fatty acids comprising the ordinary soapand soap products of commerce. Further objects will hereinafter appear.

According to the present invention it has been found that a fatty acidderivative such as soap or vegetable oil is stabilized againstdeterioration and development of rancidity by having incorporatedtherein a small proportion of a thiocyanate (or isothiocyanate). In thedescription following it is to be understood thatuniess otherwiseindicated the term "thiocyanate includes the isomeric isothiocyanates.

More particularly the present invention comprises the use of compoundscontaining one or more monovalent negative radicals consisting of theelements sulfur, carbon and nitrogen. Compounds wherein the valence ofsaid negative radical is satisfied by either an organic or inorganicradical have been found to be effective stabilizers for the class ofproducts defined above. For use with water soluble salts of fattyacids, 1. e. for ordinary soaps employed as detergents and the like,alkali metal thiocyanates are astonishingly effective and are especiallydesirable due to their ready compatibility with the soap and tolerancefor the alkaline soap medium. Ammonium thlocyanate while a. goodstabilizer has a tendency to impart a slight ammonia odor to the soap.Likewise the more volatile organic thiocyanates and isothiocyanatesbetter known as mustard oils, are generally less desirable for use inordinary soaps than solids and less volatile oils.

As one method of testing the stabilizing properties of the preferredclass of materials, the following procedure was employed:

A substantially neutral soap was prepared by saponifying a mixture ofsubstantially three parts of an edible tallow and substantially one partof cocoanut oil with sodium hydroxide. Substantially 0.1% based on theweight of the soap of one of the stabilizers of this invention wasincorporated therein by a suitable means. Five grams of the treated soapwere placed in a 250 c. c. iodine flask together with a piece of filterpaper which had been saturated with water and tom to small pieces. Theflask was then tightly stoppered and placed in an oven maintained at aconstant temperature of C. At the end of each day the color of the soapunder test was noted, also the stopper was removed and any odorindicative of rancidity noted. Similar tests were carried out with thesame soap but to which no stabilizer was added, and the periods ofstability compared as hereinafter set forth.

As specific examples and as specific embodiments of the presentinvention but in no sense to be understood as limitative of the scope ofthe invention, the following materials were incorporated in a soap ofthe above characteristics and tested in the manner described. The periodof stability or the period during which the soap did not developrancidity or materially discolor is given in the following table.

Table Percent of stabilizing Period of Stabilizing agent agent based onstability, the weight of days the soap Potassium thiocyanato 0, 1 0Sodium thiocyanate O. l Ammonium thiocyanate 0. 1 24 Guanidinethiocyanate 0. l 50 Phcnyl mustard oil l 0.1 19 Alpha naphthyi mustardoil O. l 32 Morcurous thiocyanate... 0. l 29 Ethylene dithiocyanate O. l38 Benzyl thiocyanate- 0. 1 26 Ethyl thiocyanate O. 1 l0 n-Butyithiocyanate 0. l 10 Blank No stabilizer 5 As further illustrative of thedesirable properties of the preferred class of stabilizers substantially0.1% of sodium thiocyanate was incorporated into a soap of thecharacteristics hereinbefore described and the soap so treated exposedto ultra violet light and compared with similarly exposed soapcontaining no added stabilizer. After forty-eight hours exposure theuntreated soap exhibited a surface layer of appreciable depth which hadbadly discolored, the discoloration ranging from a yellow to brown.However, the soap containing the small proportion of sodium thiocyanateshowed no discoloration wh'atsoever after forty-eight hours exposure to'ultra violet light and presented a surface to all appearances identicalwith the freshly made soap.

From the data set forth it is readily apparent that thiocyanatesconstitute an important class of soap stabilizers.

I! convenient or desirable mixtures 01 thiocyanates may be employed togood advantage as stabilizers of iatty acid derivatives such as soap andsoap products.

The amount of the selected one or mixture of the preferred substanceswhich may be added to the ordinary soap, or soap stock or ingredientsused in the manufacture thereof, for eflecting desirable results, may bevaried, but in genoral it will be found that good results may beobtained by adding, upon a weight basis from 3.531% to 1.0% of thestabilizing agent to the soap or soap stock.

In utilizing the present invention the stabilizing agent may beintroduced at any stage in the process of soap manufacture. For exampleafter the fatty acid has been obtained in the usual manner and has beensaponiiled to produce a soap stools, one or more of the stabilizers ofthis invention may be incorporated therein. The soap product may bedried in the usual manner and may be marketed in cakes, flakes or anyother form as may be desired. Further, desired the stabilizing agent maybe incorporated into the dry soap in the well known or 'ohing prooess.Moreover, the stabilizing ay conveniently be added to the oils, fatsonates oi the present invention may be employed in conjunction withsoaps and fatty oils broadly as stabilizers thereof.

Asain other methods or testing the stability of iatty acid compoundsthan those specifically disclosed may be employed, as is well known tothose skilled in the art to which the present in vention pertains.

The present invention is limited solely by the claims attached hereto aspart of the specification.

What is claimed is:

l. A soap stabilized against deterioration and development of rancidityby having incorporated therein a small proportion of an alkali metalthiocyanate.

2. A soap stabilized against deterioration and development of rancidityby having incorporated therein a small proportion of sodium thiocyanate.

3. A soap stabilized against deterioration and development of rancidityby having incorporated therein a small proportion of potassiumthiocyanate.

d. A soap stabilized against deterioration and development of rancidityby having incorporated therein a small proportion of guanidinethiocyanate.

5. A soap stabilized against deterioration and development of rancidityby having incorporated therein a small proportion of a compound selected from the group consisting of alkali metal and ammoniumthiocyanates, mercury thiocyanate, alkyl thiocyanates, guanidinethiocyanate and aryl mustard oils.

